AFTER TWO LARGE ANNUAL GAINS, RATE
OF ATMOSPHERIC CO2 INCREASE
RETURNS TO AVERAGE, NOAA REPORTS

March
31, 2005 ó A spike in the amount of carbon dioxide released into the
atmosphere between 2001 and 2003 appears to be a temporary phenomenon
and apparently does not indicate a quickening build-up of the gas in
the atmosphere, according to an analysis by NOAA climate experts. Carbon
dioxide (CO2) is released into the atmosphere by the burning of wood,
coal, oil and gas. Increases in the amount of CO2 in the atmosphere
are of special interest to scientists because carbon dioxide is a significant
heat-trapping greenhouse gas. (Click NOAA image for larger view
of carbon cycle greenhouse gases monitoring programs around the world.
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As measured
in air samples collected from more than 60 sites in the NOAA
Global Cooperative Observing Network, the amount of CO2 in the atmosphere
increased by nearly 5 parts per million (ppm) between 2001 and 2003.
The increase in 2002 was 2.43 ppm; the increase in 2003 was 2.30 ppm.
In other words, more than two additional carbon-dioxide molecules were
added to each million molecules of air each year during that period.
The annual increase was higher than the long-term average annual CO2
increase of approximately 1.5 ppm.

Included
in the global average carbon dioxide measurements are those from the
NOAA Mauna Loa Observatory in Hawaii where the CO2 record is the world's
longest continuous observations of atmospheric carbon-dioxide levels,
having begun in 1958.

The increased
CO2 levels interested scientists who questioned whether some unknown
mechanism might be causing the atmosphere to retain higher levels of
CO2.

However,
according to David Hofmann, director of the NOAA
Climate Monitoring and Diagnostics Laboratory in Boulder, Colo.,
the rate of carbon-dioxide increase returned to the long-term average
level of about 1.5 ppm per year in 2004, indicating that the temporary
fluctuation was probably due to changes in the natural processes that
remove CO2 from the atmosphere.

Global
combustion of fossil fuels and other materials places almost 7 billion
tons of carbon, in the form of CO2, into the atmosphere each year. On
average, Earth's oceans, trees, plants and soils absorb about one-half
of this carbon. The balance remains in the air and is responsible for
the annual increase.

Most of
the variability in the year-to-year CO2 uptake is related to natural
processes, including droughts and fires as well as such factors as global
temperatures, rainfall amounts and volcanic eruptions.

Understanding
these processes is key to forecasting annual CO2 increases, thus providing
important information for future CO2 management. NOAA's Carbon Cycle
Research Program, which includes surface-, ocean- and space-based measurements
of CO2 and other important atmospheric gases, is aimed at developing
a comprehensive picture of how CO2 is stored and released. The carbon-cycle
studies are a part of NOAA's Climate Program, an integral part of the
U.S. Climate Change Science Program.

"Reducing
scientific uncertainties of carbon sources and sinks is a priority for
the Climate Change Science Program, as carbon dioxide is the single
largest forcing agent of climate change," said James
R. Mahoney, NOAA deputy administrator and CCSP director.

NOAA scientists
have been tracking CO2 levels around the world for more than 25 years.
The oldest record comes from the Mauna Loa Observatory, which is located
atop a Hawaiian volcano. There, Charles Keeling began CO2 measurements
in 1958. Following NOAA's formation in 1970, measurements continued
at Mauna Loa and began at other places around the world. There are now
more than 60 monitoring sites worldwide.

Mahoney
adds, "The measurement capabilities established at NOAA's Mauna
Loa and other sites around the world demonstrates the importance of
observational networks as a contribution to understanding the complexities
of the carbon cycle."

Each year
since global measurements of CO2 began, the amount of carbon dioxide
in the atmosphere has increased.

Scientific
measurements of levels of CO2 contained in cylinders of ice, called
ice cores, indicate that the pre-industrial carbon dioxide level was
278 ppm. That level did not vary more than 7 ppm during the 800 years
between 1000 and 1800 A.D.

Atmospheric
CO2 levels have increased from about 315 ppm in 1958 to 378 ppm at the
end of 2004, which means human activities have increased the concentration
of atmospheric CO2 by 100 ppm or 36 percent.

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